Hello everyone,
I have a technical question that comes up repeatedly in my work with machine components: Why do Malm screws loosen over time, even though they were tightened correctly? I understand that screws can generally loosen due to vibrations or mechanical stresses, but with Malm screws, this issue seems to occur more frequently and sometimes even faster. Are there structural or engineering reasons that promote loosening? Is it a material issue, a design flaw, or do installation and environmental factors play a bigger role? I would like to understand if there are preventive measures to stop these screws from loosening and which physical or mechanical processes are involved. Thank you in advance for your insights and experience!
I have a technical question that comes up repeatedly in my work with machine components: Why do Malm screws loosen over time, even though they were tightened correctly? I understand that screws can generally loosen due to vibrations or mechanical stresses, but with Malm screws, this issue seems to occur more frequently and sometimes even faster. Are there structural or engineering reasons that promote loosening? Is it a material issue, a design flaw, or do installation and environmental factors play a bigger role? I would like to understand if there are preventive measures to stop these screws from loosening and which physical or mechanical processes are involved. Thank you in advance for your insights and experience!
As an addition: The preload of a bolt must permanently withstand friction and vibration forces. If these forces are exceeded, self-loosening can occur. In research and practice, devices such as the 'tooth lock washer' or 'locking washer with cams' are commonly used for this purpose.
You should also consider whether tightening is done with a torque wrench and whether temperature differences occur during tightening and operation. The latter can cause stresses that may slightly loosen the bolt again.
Overall, the better the preload and the friction in the thread, the less likely the bolt is to loosen.
You should also consider whether tightening is done with a torque wrench and whether temperature differences occur during tightening and operation. The latter can cause stresses that may slightly loosen the bolt again.
Overall, the better the preload and the friction in the thread, the less likely the bolt is to loosen.
In addition to the previous posts, I would like to point out the importance of the surface roughness of the nut and bolt. Higher roughness can improve friction but can also lead to uneven tightening, which in turn causes differences in stress.
The installation position of the bolt also plays a role: bolts are more likely to loosen under angled or eccentric loads. Therefore, proper alignment and regular inspection are essential.
Finally, the use of thread-locking compounds combined with regular maintenance is the best safeguard against this issue.
The installation position of the bolt also plays a role: bolts are more likely to loosen under angled or eccentric loads. Therefore, proper alignment and regular inspection are essential.
Finally, the use of thread-locking compounds combined with regular maintenance is the best safeguard against this issue.
Garry schrieb:
Higher roughness can improve friction, but it can also cause uneven tighteningThat is correct, which is why manufacturers often offer thread cutting tools and smoothing processes to find a balance between friction and even force distribution. Lubrication should not be overlooked either: not every bolt should be tightened dry, as excessive friction can lead to incorrect preload.
glamo schrieb:
The so-called 'creep' in the material, especially at high temperatures or under continuous loadThis causes the preload to decrease even without external mechanical influence. This is particularly important to consider with aluminum alloys or when used in warm environments.
Conclusion: Optimal preload, appropriate surface treatment, locking mechanisms, and regular inspections are necessary to prevent Malm bolts from loosening.
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